The present invention may be used in general with cup-shaped caps attachable to hollow circular members, such as fill pipes or similar means connected with fuel tanks of various kinds, stationary or mobile. It is particularly adapted for use with caps and fill pipes associated with fuel oil tanks and the like, and especially in situations where the fill pipe is disposed exteriorly of a residence or other building and normally is adapted to be manually removed. Various means have been employed heretofore to lock such caps upon the fill pipes to prevent children or other unauthorized persons from removing the cap. One means which has been employed comprises having a lock of suitable type installed in the cap and operable by a key. Even if the lock is the type which might be operated by a master key carried by the oil deliveryman, it, nevertheless, necessitates the deliveryman having the key at the time of delivery, and particularly if the key is not of the master type, it requires the deliveryman to carry a great quantity of keys and this is too much of a nuisance and is otherwise unworkable for practical purposes. Therefore, to a large extent, no practical means presently are employed in the oil delivery field or the automotive field for locking caps upon delivery pipes, except by using a key. A tight fit of the cap upon the fill pipe which requires a wrench to loosen the same is the system commonly employed at present, but there is still a need for locking the cap upon the fill pipe and the purpose of the present invention is to supply a practical means to fill that need.
Another problem incident to the oil delivery business comprises the fact that when snow of any substantial depth surrounds the fill pipe and cap, it is necessary for the deliveryman to find the cap, remove it, and frequently the cap is lost in the snow and it has been found from practical experience that each year many caps are lost in this manner and are not recovered until the snow melts to reveal the cap. Accordingly, the present invention includes means to obviate such difficulty.
In the prior art, key-operated caps or closures have been developed heretofore. One example of this structure is disclosed in U.S. Pat. No. 738,917 to Kempien, dated Sept. 15, 1903.
In recent years, there has been considerable development in the closure industry to develop child-proof caps for medicine bottles which can be operated by adults who are capable of reading the instructions on the caps which indicate how the cap may be removed but simple rotation of the cap is ineffective to do so when an attempt to unscrew the cap is made by children. Typical examples of devices of this type are shown in the following U.S. Patents:
______________________________________ 2,847,139 Christiansson et al Aug. 12, 1958 2,921,705 Dorsey Jan. 19, 1960 3,376,992 Klapp, Sr. April 9, 1968 3,426,930 Hirschler Feb. 11, 1969 3,735,887 Morris May 29, 1973 ______________________________________
In view of the fact that the present invention is concerned with the employment of magnetic means to actuate the locking mechanism, review of the prior art has developed only U.S. Pat. No. 3,060,786 to Flower, dated Oct. 30, 1962, in which a nut threadably connected to a bolt which extends commonly through two plate members to secure the same together employs magnet means to actuate a clutch which is movable upon the nut between locking and unlocking positions for purposes of either preventing rotation of the nut or rotating it when desired to remove the same from the bolt.
Additional prior U.S. Pat. No. 3,782,147 to Hallmann, dated Jan. 1, 1974, discloses a magnetically-operated safety lock, and U.S. Pat. No. 3,837,525 to Kobayashi, dated Sept. 24, 1974, discloses a case having a magnetic lock means.